Study of antigen (Ag)-specific T cell responses poses formidable technical challenges [Kern, Trends Immunol. 26:477, 2005]. This is mainly due to the fact that Ag-specific fractions are commonly represented at very low frequencies in peripheral blood, a feature which makes their detection troublesome [Mallone, Clin. Immunol. 110:232, 2004]. This detection is even more problematic when CD4+ T cells are considered, as these fractions are frequently present at even lower frequencies than their CD8+ counterparts [Homann, Nat. Med. 7:913, 2001; Seder, Nat. Immunol. 4:835, 2003]. Several detection strategies are currently available which allow to detect such Ag-specific T cells (CD4+ and CD8+) using a variety of structural or functional readouts [Kern, Trends Immunol. 26:477, 2005]. However, one drawback shared by all techniques is that Ag-specific CD4+ T cells can rarely be detected directly ex-vivo. Most commonly, these cells need to be preliminarily expanded through 5-14 d in vitro culture steps to reach the detection threshold [Mallone, Clin. Immunol. 110:232, 2004]. Recently, it was discovered that it is possible to stimulate Ag-specific T cell responses by co-culturing them with differentiating dendritic cells directly from unfractionated whole blood or peripheral blood mononuclear cell (PBMC) samples, using appropriate cytokine cocktails and culture conditions (WO 2010/119033 and Martinuzzi, Blood 118:2128, 2011). The method (named acDC technology), which provided considerable advantages, consists in a) culturing a blood or PBMC sample in a medium which comprises GM-CSF and IL-4 in the presence of an antigen, and then b) maturing the DCs with a cocktail of molecules such as tumor necrosis factor (TNF)-alpha, prostaglandin (PG)E2 and interleukin (IL)-1beta.